ISS Technology Focus, Number 14

power to DC. The severity of the power loss depends on the equipment. DC power
distribution improves safety, minimizes electrical losses, and improves data center
efficiency. As shown in the previous figure, DC power is isolated from the 480 V AC
supplied by the utility. This is much safer for personnel servicing equipment because arc
flash is not a concern. DC power distribution also requires fewer conversions from the utility
to the server components, which increases efficiency.
DC and AC power supplies
For several years, -48 V DC power supplies were more efficient than AC power supplies.
But today‟s AC power supplies, such as the HP Gold and Platinum Common Slot Power
Supplies, achieve efficiencies that reach or exceed 90%. In particular, HP Platinum
Common Slot Power Supplies reach 94% efficiency at 50% load. So, the power efficiency
advantage has now gone to AC power supplies.
Tip: Check Hyper-Threading status remotely using Microsoft® Windows® PowerShell
Intel
®
Xeon
®
four-core processors based on the Intel Microarchitecture Nehalem re-
introduced support for Hyper-Threading (HT) Technology, also known as simultaneous
multi-threading. HT, which is enabled by default, allows the OS to schedule two
instruction threads to each core to share its physical resources. HT can boost the
performance of some workloads, such as Internet and e-commerce applications, by as
much as 30%. But HT can also decrease the performance of applications, such as HPC,
that have high thread contention for the core‟s resources. For this reason, you may have
disabled HT Technology on some servers through the ROM Based Setup Utility (RBSU).
But in environments with hundreds or thousands of servers, it‟s difficult to remotely
determine which servers are HT-disabled. The most common options are:
•
Reboot each server and check the HT status through the RBSU
•
Log in to the remote console of each server and check its Task Manager.
Both options are time-consuming. A better way to check if HT is disabled for processors
running Windows Server 2008 or Windows Vista® is to use Windows PowerShell.
PowerShell is a task automation framework. It consists of a command-line shell and
associated scripting language built on top of the .NET Framework. PowerShell provides
full access to Windows Management Instrumentation (WMI), enabling administrators to
perform tasks on local and remote servers. PowerShell scripting lets administrators
automate queries to remote servers using a comma-separated list of computer names.
To query a remote computer about the HT status of its processors, use the
Win32_Processor association class:
Get-WmiObject Win32_Processor; add -computername whatever (replace whatever with
a comma-separated list of computer names)
Each instance of Win32_Processor is a socket with properties that include
NumberOfLogicalProcessors and NumberOfCores. The NumberOfCores value
represents the number of cores for the current instance of the processor. If HT is enabled
in the BIOS for the processor, then NumberOfCores is less than
NumberOfLogicalProcessors. To determine the total number of processor instances
associated with a computer system object, use the Win32_ComputerSystemProcessor
association class.
Additional resources
»
Microsoft Windows PowerShell
»
Win32_Processor class